626 STAFF COMMANDER E. W. CREAK ON THE DEVIATIONS OF THE 
2. A large proportion of the semicircular deviation may be reduced to zero, or 
corrected for all magnetic latitudes, by fixing a bard steel bar magnet or magnets in 
the compass pillar in opposition to and of equal force to the forces producing that 
deviation. 
3. A very small proportion of the semicircular deviation is due to sub-permanent 
magnetism, which diminishes slowly by lapse of time. 
4. The sub-permanent magnetism produces deviation in the same direction as the 
permanent magnetism in hard iron, except when temporarily disturbed, (1) by the 
ship’s remaining in a constant position with respect to the magnetic meridian for 
several days, (2) by concussion, (3) or by both combined, when the disturbance is 
intensified. 
5. To ascertain the full value of changes in the sub-permanent magnetism, observations 
should be taken immediately on removal of the inducing cause. 
6. In the usual place of the standard compass the deviation caused by transient 
vertical induction in soft iron is small, and of the same value (nearly) for ships of 
similar construction. 
7. The preceding conclusions point to the conditions which should govern the 
selection of a suitable position for the standard compass with regard to surrounding 
iron in the ship. 
